The frigatebird, sometimes called the man-o’-war bird, is a family of large seabirds found soaring high above tropical and subtropical oceans. They are recognizable by their long, pointed wings, deeply forked tail, and the striking red gular pouch males inflate during courtship. With the largest wing area to body mass ratio of any bird, frigatebirds spend most of their lives aloft, utilizing exceptional gliding ability to ride wind currents. This dependence on air currents directly shapes their foraging strategy, which is unlike that of most other seabirds.
Main Prey Items
The frigate bird’s primary diet consists of small fish and cephalopods, particularly squid, snatched from the water’s surface. They especially target species that swim near the surface or briefly breach the water, most famously flying fish. These fish are often caught mid-air as they glide to escape larger, subsurface predators like tuna or dolphins, which drive the prey upward. Frigatebirds are opportunistic foragers, also consuming smaller items like jellyfish, crustaceans, or plankton near the water line, and occasionally taking discarded fish from vessels.
Aerial Hunting Techniques
Frigatebirds must catch all meals in the air or just off the surface because their feathers lack the oil-coating found in most seabirds, causing them to become waterlogged if they land on the ocean. Their active hunting method, known as surface snatching or dipping, involves rapidly descending to grab prey with their long, hooked bills. This snatching is restricted to the first few centimeters immediately above or below the water line, requiring precise timing and maneuverability. Frigatebirds frequently associate with schools of large marine predators, relying on the feeding activity of tuna or mahi-mahi to force smaller fish to the surface. This cooperative foraging ensures a steady supply of accessible prey, minimizing the energy expenditure of searching over the open ocean.
The Role of Kleptoparasitism
Frigatebirds are known for a specialized feeding behavior called kleptoparasitism, which translates to “parasitism by theft” and involves deliberately stealing food from other animals. They use their superior speed and aerial agility to harass other seabirds, such as boobies, gulls, and terns, until the victim is forced to drop or regurgitate its recently caught meal. The frigatebird then deftly swoops down to catch the food in mid-air before it hits the water. While this behavior is a significant part of their reputation, it is generally considered a supplementary strategy rather than the foundation of their diet. Studies suggest that kleptoparasitism typically accounts for only a small percentage, sometimes as low as five percent, of a frigate bird’s total food intake.
Dietary Influence on Habitat
The frigate bird’s specialized diet and physical limitations dictate their foraging range and habitat preferences. Because they cannot rest on the water, they must remain within flying distance of land or reliable updrafts to sustain their flight. Consequently, they forage over tropical and subtropical waters where surface prey is abundant and conditions favor their soaring flight style. They concentrate foraging efforts in areas where oceanographic features, such as upwellings, naturally concentrate prey close to the surface. While they are highly pelagic and can travel up to 500 kilometers from their colony, the need for accessible surface prey and coastal nesting sites restricts their distribution to tropical island regions, causing them to avoid the vast, open ocean where prey is less predictable.